Document automated tests

2 files changed, 44 insertions, 2 deletions

diff --git a/doc/index.md b/doc/index.md
index 293e6611..8ba03a31 100644
--- a/doc/index.md
+++ b/doc/index.md
@@ -2,12 +2,13 @@
 
 ## Projects we pull from
 
-There are currently 4 products that are pulled and generate the docs website:
+There are currently 5 products that are pulled and generate the docs website:
 
 - [GitLab](https://gitlab.com/gitlab-org/gitlab)
 - [Omnibus GitLab](https://gitlab.com/gitlab-org/omnibus-gitlab)
 - [GitLab Runner](https://gitlab.com/gitlab-org/gitlab-runner)
 - [GitLab Chart](https://gitlab.com/gitlab-org/charts/gitlab)
+- [GitLab Operator](https://gitlab.com/gitlab-org/gitlab-operator)
 
 NOTE:
 Although GitLab Community Edition is generated, it is hidden from the website
@@ -36,7 +37,7 @@ There are multiple ways to preview GitLab documentation changes, you can:
 ## Develop and maintain the docs site
 
 If you are interested in making contributions to the GitLab documentation site itself,
-see the [GitLab docs site development](development.md) page.
+see the [GitLab docs site development](development.md) and [Testing the GitLab docs site](testing.md) pages.
 
 GitLab technical writing team members sometimes have to do maintenance tasks:
 
diff --git a/doc/testing.md b/doc/testing.md
new file mode 100644
index 00000000..bb0e5497
--- /dev/null
+++ b/doc/testing.md
@@ -0,0 +1,41 @@
+# Testing the GitLab docs site
+
+Before any changes to the `gitlab-docs` project are merged, they are tested in a merge request's
+CI/CD pipeline. The pipeline configuration is in the [`.gitlab-ci.yml`](../.gitlab-ci.yml) file.
+
+You can [run the same tests locally](#run-tests-locally), before pushing your changes
+to the project.
+
+## What do we test?
+
+| Test target  | Tool        | Purpose             |
+| ------------ | ----------- | ------------------- |
+| CSS          | Stylelint   | Code quality        |
+| Dockerfiles  | Hadolint    | Syntax checks       |
+| JavaScript   | ESLint      | Syntax checks       |
+| JavaScript   | Prettier    | Code formatting     |
+| Links        | Nanoc check | Find broken links   |
+| Ruby         | RSpec       | Unit tests          |
+| Vue          | Jest        | Unit tests          |
+| YAML         | yamllint    | Syntax checks       |
+
+## Run tests locally
+
+You must install the dependencies before you can run tests locally:
+
+- node modules: `yarn install`
+- Ruby gems: `bundle install`
+- hadolint (MacOS: `brew install hadolint`)
+- yamllint (MacOS: `brew install yamllint`)
+
+To run the tests:
+
+`make test`
+
+### Lefthook
+
+Optionally, you can use Lefthook to automatically run tests before pushing code.
+Install Lefthook with `lefthook install`, then the tests run each time you run a
+`git push` command
+
+Lefthook settings are configured in [`lefthook.yml`](../lefthook.yml).